Multiphase DC-DC converters that have a configuration in which a plurality of voltage conversion units are connected in parallel to each other are known as DC-DC converters that drive switch elements to step up or down a DC voltage. Examples of this type of multiphase DC-DC converter include a technique as disclosed in JP 2013-46541A.
Meanwhile, in such a multiphase DC-DC converter, there may be a case where only one phase fails, and if one phase fails, it may be preferable to continue the operation using a phase that has not failed, instead of halting the entire operation of the DC-DC converter. A power supply device of JP 2013-46541A addresses this need, and is configured to acquire electric current values that are detected by an electric current detector at timings of falling edges of control signals that are applied to switch elements of respective phase chopper units, and to determine that one of the phase chopper units has failed if the acquired current values are different. Even if it is detected that one of the phase chopper units has failed, the operation of a phase chopper unit that has not failed is continued, and an output of a power generator is restricted so as not to exceed a withstanding electric current of the phase chopper unit that has not failed.
However, the power supply device of JP 2013-46541A merely restricts the entire output if an open-circuit fault has occurred in any of the switch elements of the phase chopper units, and does not include the idea of correctly identifying a portion where the fault has occurred, and reliably disabling the operation of this portion.
The present invention was made in view of the above-described circumstances, and it is an object thereof to provide a multiphase converter that is provided with a plurality of voltage conversion units, and has a configuration in which, if an abnormality has occurred in any phase, the multiphase converter can be kept activated with a phase other than the faulty phase while the faulty phase is reliably protected.